JPH02156740A - Optical information transmission equipment - Google Patents

Abstract

PURPOSE:To reduce the radiation intensity of an optical transmitter by applying weighting to a directivity of a light receiving characteristic of an optical receiver in an optical information transmitter sending optical information from the optical transmitter through spatial transmission. CONSTITUTION:An optical means such as a lens or a reflecting mirror is fitted to a photodetector of a light receiver of an optical receiver A. Moreover, weighting in response to an angle X representing the direction of an optical transmitter B is applied to a vertical direction directivity (nondirectivity in horizontal direction) of the light receiving characteristic. Thus, the radiation illuminance of the light reaching the photodetecting element of the photodetector of the optical receiver A is uniformized regardless of the location of the optical transmitter B.

Description

[Detailed description of the invention] (Industrial application field).

The present invention relates to an optical information transmission device that transmits optical information by spatial transmission from an optical transmitter located at an arbitrary position within a predetermined space to an optical receiver fixedly installed at a predetermined position within the predetermined space.

(Prior Art) Conventionally, spatial transmission of optical information within a premises (within a predetermined space) using light such as infrared rays has been carried out by installing an optical transmitter/receiver (omnidirectional) A on the ceiling of the room, as shown in Figure 9. A method has been put into practical use in which optical information (data) is transmitted between fixedly installed terminals and an optical transceiver B on the terminal side located at any position in the room by spatial transmission [Institute of Electronics and Communication Engineers]. Communication Method Study Group Material 36 1982 J C382-83 (P57-64
) "Optical wireless modem for office communication").

However, this method requires an optical transmitter/receiver (
Since the directivity of the light intensity (11104 intensity) to the optical transmitter/receiver on the terminal side (in this case, the focus is on the function as an optical transmitter) is omnidirectional, the focus is on the function as an optical receiver (in this case, the focus is on the function as an optical receiver). ) The light illuminance (irradiance) obtained on the optical transceiver B side changes depending on the installation position of the receiving (light receiving) terminal head of B.

Therefore, the radiation intensity to the optical transceiver (optical transmitter) is the irradiance required for the reception terminal head of optical transceiver (optical receiver) B installed at the farthest position from directly below the optical transceiver. It is necessary to set it to give .

Therefore, the conventional method of making the radiation intensity of the optical transceiver A omnidirectional is wasteful in terms of energy efficiency.

Therefore, in order to solve the above problems, the applicant first developed an optical transceiver (optical receiver) so that the optical transceiver B could obtain uniform irradiance regardless of the position of the optical transceiver (optical receiver) B. We proposed an optical information transmission system@j in which the directivity of the radiation intensity of optical transmitter A was weighted, and filed a patent application on March 20, 1986 (Japanese Patent Application Laid-Open No. 63-232720). 62-
No. 66531)).

Regarding the light receiving device of the conventional optical transmission system, as shown in Fig. 10, a light receiving element (phototransistor)
In front of 1, there is a U-shaped anti-DIifl that combines two reflective surfaces 2 and 3 formed into a three-dimensional surface by rotating a part of an ellipse, and has a wide directivity and high light-receiving sensitivity (special 1972-28908).

In addition, as shown in FIG. 11, a plurality of photo diodes p having a light-receiving sensitivity of 0.5 at a half-power angle of 60° and a spherical directional characteristic of light-receiving sensitivity are arranged, for example, Three photodiodes p as shown in the figure
＋”=The composite directional characteristics created by combining the directional characteristics created by p3 are combined into an almost circular shape to create omnidirectional (3
60") that provides a wide-angle light receiving area (Japanese Patent Laid-Open No. 59-238).

(Problems to be Solved by the Invention) By the way, the paging system, which is a spatial transmission system of optical information within a premises (within a predetermined space) using light, uses an optical transmitter/receiver (hereinafter referred to as this) as a base unit. Since we are focusing on the function as an optical receiver (optical receiver),
A) is usually fixedly installed in the center of the ceiling of the room, and an optical transmitter/receiver (hereinafter referred to as an optical transmitter (light emitter) of this) is attached.
Since we are focusing on its function as an optical transmitter, the optical transmitter (hereinafter referred to as "optical transmitter") B is configured to transmit data from an arbitrary position within the room to the optical receiver A, which is a main unit.

Therefore, if the optical receiver (base unit > Alfi omnidirectional),
The tllai intensity of the light transmitted from optical transmitter (child 1) B is such that the transmission from optical transmitter (child unit) B installed at the farthest position from directly below the optical receiver (base unit) can be received. It is necessary to set it so that

However, if the radiation intensity of optical transmitter (slave unit) B is set in this way, optical reception will be affected if optical transmitter (slave unit) B is directly below or around the optical receiver (base unit). This will give the device (base unit) A more radiation intensity than the required amount. That is, the radiation intensity (amount of light emitted) of the optical transmitter (slave device) B exceeds the required m in most of the room, which is extremely inefficient and wasteful in terms of efficient energy use.

Furthermore, since the optical transmitter B, which is a slave device, relies on a battery for its power source due to the need for portability, there is a demand to keep the radiation intensity (light emission amount) as low as possible. Therefore, it is necessary to reduce such energy waste as much as possible.

Furthermore, the light receiving device shown in FIG.
! This corresponds to the case where the i (light transmitting) side is fixedly installed at a specific position, so the optical receiver 2! which is the base unit of the paging system! ! It is not suitable as a light receiving device in 8.

Therefore, the present invention solves the problems of the conventional technology described above,
It is an object of the present invention to provide an optical information transmission device that can significantly reduce the radiation intensity of an optical transmitter compared to conventional devices.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an optical receiver fixedly installed at a fixed position within a predetermined space, and an optical transmitter located at an arbitrary position within the predetermined space. In an optical information transmission device that transmits optical information by spatial transmission, the light-receiving characteristics of the optical receiver are adjusted so that the light-receiving element of the optical receiver receives uniform irradiance regardless of the position of the optical transmitter. The present invention provides an optical information transmission device characterized in that the directivity is weighted.

Further, in the optical receiver in this optical information transmission device, the angle between the vertical direction centered on the optical receiver and the direction of the optical transmitter is X, and the angle between the vertical direction and the direction of the optical transmitter is X. When the maximum value of the angle is set to Xll1ax, the pitch Yx of the vertical directivity of the light receiving characteristic of the optical receiver is given by the following formula (where P is a constant).

(Function) In the optical information transmission device configured as described above, an optical transmitter located at an arbitrary position within a predetermined space emits a constant radiation intensity, so that the optical receiver can be activated regardless of the position of the optical transmitter. A uniform irradiance Lq is applied to the light receiving element.

(Example) In order to explain the present invention, first, a slave unit (optical receiver) in a conventional example in which the base unit (optical receiver) has omnidirectional light receiving characteristics will be explained.
The waste of the radiation intensity (light emission m) emitted by the optical transmitter) will be described, and then the light receiving characteristics of the present invention will be quantitatively described.

A room not shown in Figure 1 is used as a model, and an optical receiver with a light receiver whose characteristics are suitable for MAN is placed in the center of the ceiling of the room. f
f) Determine the tIi error intensity required for the optical transmitter (slave device) B at each position in the room when A is fixedly installed.

In the same figure, an optical receiver (master unit) A and an optical transmitter (child 1f
The distance between f>8 is the shortest when optical transmitter (child unit) B is at position 81, that is, when optical receiver (parent unit 1)
This is the case where it is directly under A. In this case, the light radiation intensity (1) required from the optical transmitter (child B) is determined as follows.

1+/H2=, where K is the irradiance sensitivity of the receiver (minimum receivable
1a4 illuminance), and H is the shortest path M (vertical distance) between the optical receiver A and the optical transmitter B.

Therefore, 1+= to -82...(1) becomes.

Next, optical transmitter (child unit) B when optical transmitter (child unit 1) B is located at a position ex away from directly below optical receiver (master unit) A.
The required emission intensity (amount of light emitted) Ix to be emitted is as follows: lx/(L2+H2)=. However, L is the distance between B1 and 8x.

Therefore, lx = K・(L2+112) = K 4 t1 2 − sec 2 X
-(2). However, X is the angle [in radians] between the vertical direction centered on the optical receiver (parent+1) A and the direction of the optical transmitter (slave device) B. 1 (1), When calculating the ratio M of both radiation intensities from equation 0, we get M
= lx /I + =sec2X ・(
3). From this equation (3), the following can be said. In other words, the radiation intensity required for optical transmitter i8 (child 1) B increases as the distance from position 81 directly below optical receiver (parent TFL) A increases, and from position 82 (optical receiver A) where X is maximum,
It is maximum at the position farthest from directly below).

Therefore, turn the entire room into a service area.
The optical transmitter (
It is necessary to set the light emission level of slave unit) B.

However, conversely, this means that if there is an optical transmitter (slave unit) B at a location other than the farthest position 82, it will always emit over-level light from there, making it inefficient. There is a lot of waste in terms of efficient use of energy.

In contrast, in the present invention, an optical means such as a lens or a mirror is attached to the light receiving element of the light receiver of the optical receiver (base unit) A, and the light receiving characteristics are vertically oriented as shown in FIG. (However, the horizontal direction is omnidirectional) and the optical transmitter (
Child 1) By taking into account the direction of B and applying weighting according to the angle This makes the irradiance uniform, eliminates the above-mentioned inefficiency, and significantly reduces the required radiation intensity of the optical transmitter (slave device) B.

Based on the diagram, first determine the required emissions of optical transmitter (slave unit) B.
The manner in which the intensity becomes uniform will be explained.

Now, when the optical transmitter (slave unit) B is in the direction 3x of the angle X from the vertical line (vertical line) centered on the optical receiver (base unit) A, the radiation intensity of the optical transmitter (slave unit) 8 is Let I be the irradiance JX of the light that reaches the optical receiver (base unit) A as follows.

Jx = I/ (H-secX)2...A
4) Now, find the directivity m of the light receiving characteristics of the light receiver of the optical receiver 3 (base unit) A at the angle X using the following formula (5) % formula %
(5) However, P is a constant, and X max is the maximum angle (the angle at the farthest position from the optical transmitter (child device) B).

Then, the irradiance Jx' of the light reaching the light receiving element of the optical receiver (base unit) A is given by the following equation 0.

Jx ' = Jx - Yx = P ・I ・ (cos It can be seen that x r is a constant value (uniform) regardless of the angle X.

1, that is, the directivity of the optical receiver (base unit) A is (0
If given by the formula, it becomes possible to make the required radiation intensity (light emission amount) of the optical transmitter (child 1) B uniform regardless of the position (location). If the receiver's /&DI illuminance sensitivity (minimum receivable illuminance) is K here, then the required minimum value Ill1in of the radiation intensity of the optical transmitter (slave unit) 8 is given by the following formula: become that way.

K=Pφlm1n −(cosXmax /H)2 Therefore, lm1n = −1−12/(P −cos2X+a
x) -C0Next, the radiation required for optical transmission "JS (slave unit) B" when using an omnidirectional light receiver and when using a directional light receiver of the present invention. Intensity (light emission amount)
The extent to which is a difference will be clarified by finding the vi of P (where P is a constant).

By the way, the light receiving characteristics can be considered in place of the light transmitting characteristics. In other words, if we apply optical means to provide the required directivity to the optical receiver (base unit) to the light emitting element of optical transmitter (slave unit) B and examine its behavior, we can determine the light receiving characteristics simply by The same result can be obtained by simply reversing the direction of travel.

Now, with respect to the vertical direction centered on the optical receiver (base unit) A, omnidirectionality is established within a cone at an angle Xmax (the angle at which the optical transmitter (slave unit) is furthest away). Consider a light emitter that does what it does and a light emitter that has directivity given by the following equation.

Here, if the radiation intensity of the light-emitting elements of each of the above-mentioned light-emitting devices is the same for the former two, the total luminous flux passing through the surface where the spherical surface centered at the center point of these light-emitting devices is cut by the above-mentioned cone is It is the same for all persons. When the radiation intensity of the light emitting element of the light emitter is set to 1, the total luminous fluxes C1 and C2 of both are determined as follows.

C+= (1-C6SX)・I/2...■
C2= (1-cosX) xl/(2P-cosXmax) -Q where,
Since Cl=C2, P is calculated using the following formula (g)% formula% If the direction is reversed, the relationship in equation (g) holds true as is.

Therefore, by substituting the relationship in equation (g) into equation 0, we get (11)
The formula is obtained.

JX' = I-COS Xmax /H2・'(
11) Here, if the required minimum radiation intensity of optical transmitter (slave unit) B is IrAin, then from equation (11), the following (12
) formula is obtained.

lm1n =K ・H2-secXmax -(
12) That is, equation (12) is an equation that gives the minimum radiation intensity required of the optical transmitter (slave unit) B when the directional characteristic of the present invention is applied to the light receiver.

On the other hand, the minimum intensity q4 required when the directional characteristic of the light receiver is omnidirectional is the value I2 obtained by substituting X max for x in the above equation 0.

12 =K ・H2-s e c2Xmax ・
-(13) Comparing equations (12) and (13), the former is secxmax times (s e CX
max is always greater than 1 and increases as X max becomes larger. That is, by imparting a predetermined directivity to the light receiver, the radiation intensity required of the optical transmitter (slave device) B is reduced, and the rate of reduction increases by b as X max increases.

Table 1 below shows a comparison between the two. However, )(max=
When o, the required radiation intensity is 1 when the receiver is non-directional.

Next, specific examples using the device of the present invention will be described below.

FIG. 3 is a diagram showing a first embodiment using the device of the present invention.

In the figure, the optical receiver (base unit) Al, which is the light receiver, is fixedly installed on the ceiling with a height of 2.5 [ml], and the optical transmitter (child 1) 8, which is the light emitter, is fixedly installed on the ceiling with a height of 1 [ml] from the floor. Optical receiver at height (
It is assumed that it is located at any position (place) within a radius of 10 [ml] from the point directly below A. That is, in FIG. 3) (OlaX = 81.5').

Therefore, eight PIN photodiodes having the directional characteristics shown in Fig. 4 are arranged at equal intervals on the circumference in the horizontal direction, and 81.5' in the vertical direction, as shown in Fig. 5. When installed at an angle of '', as shown in Figure 6,
At max, the light-receiving sensitivity is the highest, and a characteristic close to the directivity of the ideal hand-built light-receiving characteristic shown in FIG. 2 can be obtained.

FIGS. 7 and 8 are diagrams showing a second embodiment using the apparatus of the present invention. These figures show the case where the apparatus of the present invention is used in a place having a different shape from a normal room. Fig. 7 shows the use of the present invention device in a hallway, and Fig. 8 shows the use of the present invention in a staircase. In such places, taking into consideration the shape of the light transmitter (slave unit), the light receiver (light receiver) (light receiving element in main 8 The directionality is weighted so that the light with the luminous flux density reaches ml.

In Figs. 7 and 8, a shows the omnidirectional directivity (-dashed line) in which the directivity toward the optical receiver (parent II) is not weighted, and b shows the light beam in consideration of the shape of each location. The directivity characteristics (solid line) are shown in which the directivity of receiver (base unit) A is weighted. In either case, by using a non-directional light receiver for the optical receiver (base unit) A, a wide beam area can be efficiently obtained.

Note that the device of the present invention can be applied to optical information spatial transmission systems other than the above-mentioned paging system, and is an extremely effective means for expanding the service area of such systems.

(Effects of the Invention) As described above, according to the optical information transmission device of the present invention, the optical transmitter located at any position within a predetermined space emits a constant radiation intensity, regardless of the position of the optical transmitter. Since the light-receiving element of the optical receiver can obtain a uniform illuminance, the radiation intensity of the light emitted from the optical transmitter can be significantly reduced, so power consumption can be reduced, especially when batteries are used as the power source for the optical transmitter. Or you can significantly extend your life.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the optical information transmission device of the present invention, FIG. 2 is a diagram showing the directivity of the light receiving characteristics of the device of the present invention, and FIGS. 3 to 6 are diagrams for explaining the optical information transmission device of the present invention. A diagram showing the first embodiment, FIGS. 7 and 8 are diagrams showing a second embodiment using the device of the present invention, and FIG. 9 explains spatial transmission of optical information in a premises using light. 10 to 12 are diagrams showing a light receiving device of a conventional optical transmission system. A... Optical transceiver (Oyiso; optical receiver 4), B... Optical transceiver (slave device: optical transmitter), X... Angle between the vertical direction and the direction of the optical transmitter, X max: Angle at the farthest position of the optical transmitter. Figure '/, = P'CO52X1.5eC2X Figure Figure Figure Figure Date - Figure Figure Figure Figure Date

Claims (2)

[Claims] (1) In an optical information transmission device that transmits optical information by spatial transmission from an optical transmitter located at an arbitrary position in the predetermined space to an optical receiver fixedly installed at a fixed position in the predetermined space, the optical transmitter An optical information transmission device characterized in that the directivity of the light receiving characteristic of the optical receiver is weighted so that the light receiving element of the optical receiver can obtain uniform irradiance regardless of the position of the optical receiver. (2) The optical receiver in the optical information transmission device according to claim 1 is arranged such that an angle formed between a vertical direction centering on the optical receiver and a direction of the optical transmitter is X, and the vertical direction and the optical transmitter When the maximum value of the angle formed with the direction of the receiver is Xmax, the vertical directivity weighting Yx of the light receiving characteristics of the optical receiver is calculated by the following formula Yx=P・cos＾2Xmax・sec＾2X (however,
(P is a constant).